The present invention is related to a multi-component analyzing apparatus, particularly, to a mixed-refrigerant analyzing apparatus capable of analyzing refrigerant components contained in a mixed refrigerant in a separate manner.
Generally speaking, so-called “fluorocarbon” is conventionally used as refrigerants which are employed in refrigerating apparatus (cooling machines) such as, refrigerators and air conditioners. As to fluorocarbon, there is an HFC series of new refrigerants in addition to a CFC series and an HCFC series of old refrigerants. These series of fluorocarbon own various problems as to destruction of the ozone layer, and global warming trends in earth temperatures, so that there are duties to collect and recycling-use the above-described fluorocarbon. Also, such fluorocarbon which cannot be recycling-used must be firmly destroyed.
On the other hand, the fluorocarbon of R410A, R407C, R404A, and R507A which is typically known as the new refrigerants, corresponds to such mixed refrigerants which are formed by mixing several sorts of single-component fluorocarbon (R32, R125, R134a, R143a etc.) with each other in predetermined ratios. In addition, there is fluorocarbon R502 of the old refrigerant as the mixed refrigerant. On the other hand, in the case that a mixing ratio of collected fluorocarbon is not proper since fluorocarbon is collected in an erroneous manner, if this collected fluorocarbon is directly recycling-used, then there is a risk that performance of refrigerating apparatuss is deteriorated, or these refrigerating apparatuss are destroyed.
As a consequence, after fluorocarbon collecting industries have collected fluorocarbon, the collecting industries are required to confirm as to whether or not the collected fluorocarbon can be recycling-used by using such a fluorocarbon meter as described in Japanese Laid-open Patent Application No. Hei-2-124448, and then, are required to judge as to whether the collected fluorocarbon is recycle-used, or destroyed. In other words, concentration of fluorocarbon must be measured before, or after collections of the fluorocarbon in order to prevent erroneous collections and/or erroneous uses when the fluorocarbon is collected and recycling-used.
As means capable of measuring the above-described fluorocarbon concentration, the NDIR method has been proposed in, for example, the above-explained patent publication 1. In order to perform analysis of mixed refrigerants by using this NDIR method, such a mixed-refrigerant analyzing apparatus is employed. In this mixed-refrigerant analyzing apparatus, while an infrared light source is provided on one side of a cell to which a mixed refrigerant containing a plurality of refrigerant components is applied as sample gas, both a plurality of bandpass filters and a plurality of detectors are provided on the other side of this cell. The plural bandpass filters may pass therethrough infrared light (infrared rays) having wavelengths which are fitted to infrared absorption spectra of the above-explained refrigerant components-among infrared light which has passed through this cell. The plural detectors measure intensity of infrared light which has passed through these bandpass filters.
In this case, in order that a plurality of refrigerant components which constitute the mixed refrigerant may be individually detected in higher precision, infrared light transmission wavelength ranges of these bandpass filters which are provided in correspondence with the respective refrigerant components must be set in proper range conditions. In the conventional mixed-refrigerant analyzing apparatus, central wave numbers (namely, inverse numbers of wavelengths) of the above-explained bandpass filters have been determined by mainly considering such a wavelength band that infrared absorptions in the respective refrigerant components are large. For example, in the case that the single component fluorocarbon of R143a, R125, R134a, R32, R115, R12, and R22 is analyzed, as indicated in the below-mentioned table 1, the central wave numbers of the respective bandpass filters have been set.
TABLE 1unit: cm−1R143aR125R134aR32R115R12R22central wave12351215118711079819201117number
However, in the above-described conventional mixed-refrigerant analyzing apparatus, as represented in the below-mentioned table 2, measurement errors of the respective refrigerant components are very large. More specifically, as to the fluorocarbon of R32 and R22, measurement error thereof are large.
TABLE 2R143aR125R134aR32R115R12R22less1.5%less2.6%less1.5%3.9%than 1%than 1%than 1%
FIG. 19A and FIG. 19B indicate 100% absorbances of the fluorocarbon R32 and R22. As apparent from these graphic representations, such a fact can be revealed. That is, the absorbance of the fluorocarbon R32 is influenced by the fluorocarbon R22, and conversely, the absorbance of the fluorocarbon R22 is influenced by the fluorocarbon R32. In other words, these fluorocarbon R32 and R22 may have a so-called “mutual interference relationship” by which the fluorocarbon R32 and R22 may give interference influences to each other.
Also, FIG. 20 is a graphic diagram for representing both infrared absorption spectra of seven refrigerant components R143a, R125, R134a, R32, R115, R12, and R22, and also infrared transmission characteristics of the respective bandpass filters in a comparison manner. In this drawing, curves indicated by symbols “A1” to “A7” show the infrared absorption spectra of the above-described seven refrigerant components R143a, R125, R134a, R32, R115, R12, and R22, whereas curves denoted by symbols “B1” to “B7” represent the infrared transmission characteristics of the bandpass filters. As previously explained, in the conventional mixed-refrigerant analyzing apparatus, since the central wave numbers of the bandpass filters used to detect the respective refrigerant components have been set to the large infrared absorptions, namely have been set by mainly considering the low wavelength range of the infrared absorption spectra, the central wave numbers of the bandpass filters for the refrigerant components R32 and R22 have been set to such positions (values) where these central wave numbers are located in the vicinity of each other, as indicated in the curves “B4” and “B7” in FIG. 20. As a result, the measuring precision of these refrigerant components R32 and R22 is mutually deteriorated.
On the other hand, the Inventors of the present invention have filed U.S. patent application Ser. No. 10/207,783 (Publication 2003-0034454-A1) by which the simultaneous equations capable of correcting the mutual interference of the multiple components contained in the sample gas are solved so as to acquire the component ratios in such a similar case that a plurality of refrigerant components contained in a mixed refrigerant are analyzed. In such a calculation process operation is carried out, the following setting operation may constitute a very important aspect. That is, the infrared transmission wavelength ranges in the bandpass filters used to detect the refrigerant components corresponding to the measuring-subject components are set in such a manner that the desirable analysis results may be obtained.
In this measuring method, assuming now that a total number of measuring-subject components is “n”, the intensity of the infrared light having the wavelength range fitted to the infrared absorption spectra of the respective measuring-subject components of the infrared light which has passed through the measuring-subject sample is measured by the non-dispersion type infrared gas analyzing meter (NDIR gas analyzing meter) having “n” pieces of the measuring devices. Then, in this non-dispersion type infrared gas analyzing meter, the absorbances “y1” to “yn” are calculated based upon the measurement values of the respective measuring devices, and then, the analyzing operation is carried out by employing the respective absorbances “y1” to “yn”, so that the respective concentration “x1” to “xn” can be calculated.
It should be understood that since the above-explained absorbances “y1” to “yn” are defined as a logarithm of such a value obtained by subtracting measurement values of the respective detectors acquired when, for example, a measuring-subject sample is measured from measurement values acquired when zero gas is measured, attenuations of absorbances occurred by mixing the respective measuring-subject components with each other can be expressed by an addition, and thus, the subsequent calculation process operations can be carried out in a simple manner. As a result, since measurement values by the respective measuring devices may be sometimes obtained as logarithmically-calculated absorbances, it is so assumed that measurement values acquired by the respective measuring devices express the absorbances “y1” to “yn” in the below-mentioned descriptions. However, the present invention is not limited to this point.
The below-mentioned formula (1) corresponds to linear simultaneous equations which indicates one example of simultaneous equations employed so as to analyze the concentration “x1” to “xn”, and represents a summation of one-dimensional equations corresponding to the concentration “x1” to “xn” of the respective measuring-subject components. In other words, since the linear simultaneous equations are solved, the respective concentration “x1” to “xn” can be analyzed based upon the measurement values “y1” to “yn” obtained by the respective measuring devices:
                              y          i                =                              ∑                          j              =              1                        n                    ⁢                      (                                          a                ij                            ⁢                              x                j                                      )                                              formula        ⁢                                  ⁢                  (          1          )                    It should be noted that the linear simultaneous equations are made of “n” pieces (i=1 to “n”) of simultaneous equations. Symbol “i” shows a number of a detector, symbol “j” indicates a number of a measuring-object component, symbols “y1” to “yn” represent measurement values obtained from “n” pieces of the detectors which detect transmission light having different wavelength ranges from each other, symbols “x1” to “xn” show concentration as to “n” pieces of components, and symbol “aij” denotes a constant.
Also, in the simultaneous equations indicated in the above-explained formula (1), in such a case that there is no linear relationship between each of the component concentration “x1” to “xn” and a dependent variable (measurement values y1 to yn), and the respective component concentration x1 to xn cannot be approximated to the dependent variable in a linear manner, as represented in a formula (2), such non-linear simultaneous equations with employment of a polynomial higher than, or equal to a quadratic equation may be employed:
                              y          i                =                              ∑                          j              =              1                        n                    ⁢                                    (                                                                    a                    ij                                    ⁢                                      x                    j                                                  +                                                      b                    ij                                    ⁢                                      x                    j                    2                                                  +                ⋯                            ⁢                                                          )                        .                                              formula        ⁢                                  ⁢                  (          2          )                    
It should also be noted that symbols aij, bij, cij, . . . show constants, symbol “i” shows a number of a detector, and symbol “j” represents a number of a measuring-subject component.
However, since the above-described measurement values “y1” to “yn” acquired by the respective detectors are obtained in such a way that after such a infrared light having a predetermined wavelength range has been selectively penetrated by employing, for example, a plurality of optical filters among the infrared light which has passed through the measuring-subject sample, the respective detectors detect intensity of the infrared light which has passed through the respective optical filters, there is no way capable of avoiding such an event that several widths are produced in the wavelengths of the transmission light due to the filter characteristics of the optical filters. Then, the relationship between the filter characteristics of the optical filters and the infrared absorption spectra of the respective measuring-subject components may constitute an important element capable of establishing the relationship of the above-explained formulae (1) and (2).
However, as shown in FIG. 12, the infrared absorption spectra of the respective measuring-subject components own the wavelength dependent characteristics even in narrow ranges of the respective optical filters, and is overlapped with each other. As a result, such an adverse influence for distorting the filter characteristics of the above-explained optical filters is received by the infrared absorptions of other measuring-subject components mixed with each other, so that the absorbances which have been converted into the logarithms cannot become completely equal to such absorbances obtained by adding the absorbances to each other obtained by the respective measuring-subject components. Thus, there are some possibilities that errors caused by the interference influences may occur in the measurement values “y1” to “yn” detected by the respective detectors. It should be understood that in FIG. 12, symbols “Aa” to “Ag” represent infrared absorption spectra of the respective measuring-subject components, and symbols “Ba” to “Bg” show infrared transmittance characteristics of the optical filters.
FIG. 13 is a diagram for graphically indicating differences between calculation values of absorbances and measurement values of the absorbances, while these calculation values of absorbances obtained by substituting concentration of the respective measuring-subject components for the multi-dimensional (three-dimensional) simultaneous equations shown in the above-explained formula (2) when a mixing ratio of the fluorocarbon R125 and the fluorocarbon R134a as one example of the measuring-subject components is changed from 0% to 100%.
In FIG. 13, symbols “C125” and “C134a” represent calculation values of absorbances which are calculated every detector corresponding to each of the measuring-subject components by substituting concentration corresponding to a mixing ratio of the fluorocarbon R125 to the fluorocarbon R134a for the simultaneous equations. On the other hand, symbols “D125” and “D134a” indicate measurement values detected by the respective detectors when such a mixed gas of the fluorocarbon R125 and the fluorocarbon R134a is actually measured. As can be understood from FIG. 13, the largest differences between the calculation value C125 and the measurement value D125, and between the calculation value C134a and the measurement value D134a may appear when both the fluorocarbon R125 and the fluorocarbon R134a are mixed with each other in the ratio of 50 weight %. Also, a difference between the values C125 and D125 of the above-described absorbances is on the order of 0.008 at maximum, and is on the order of 2.7% with respect to the magnitude (0.30) of the absorbance.
In other words, as shown in the above-explained formula (2), in such a case that even when the quadratic equation, or higher polynomial is employed, there are mutually interference influences in the measured wavelengths of the respective components, there are some changes in outputs due to the component concentration which may cause the interference. Thus, even if the simultaneous equations as indicated in the formula (2) are solved, there are some possibilities that errors of several % happen to occur.
However, very recently, higher precision less than 1% is required for such multi-component analyzing apparatus capable of calculating concentration ratios of fluorocarbon, so that the conventional multi-component analyzing apparatus could not be suitably used in such higher precision.
Furthermore, specifically, in such multi-component analyzing apparatus, when a measurement is made of a standard sample constituted by single components, and also, another measurement is made of such a standard sample which is constituted by mixing a plurality of measuring-subject components with each other in predetermined concentration, higher precision may be required. Since a plurality of these measuring-subject components are mixed with each other in the preselected concentration, the measuring-subject components may mutually interfere with each other. As a result, there is no way to avoid such a fact that errors are increased.